It seems that when you have an input type=file element within a div that's hidden (in this case behind a previous tab prior to submitting the form) Safari (any version) hangs 5 out of 10 times. Safari is the only browser that has this "feature" and I can't imagine that I'm the only one that hides input elements behind tabs.
This bug has been bugging me since the first version of Safari and Webkit, and it would be nice if someone fixed the issue or provided me with a work-around.
It's predominantly with local file uploads.
I don't see a problem.
When does it hang? When switching the "tab"? When uploading?
Can you provide a reduced test case (e.g. a page witch hides a div with a file input) and attach it here at the bug?